1. Field of the Invention
The present invention generally relates to an electromagnetic relay and, more particularly, to a small electromagnetic relay capable of cutting-off a high voltage.
2. Description of the Related Art
Recently, the motorization of car-mounted parts (for example, sideview mirrors and seats) has been promoted. Electromagnetic relays are frequently used for controlling supply of electric power to electric motors or solenoids, which act as electrically-driven actuators. Needless to say, compactness is required of car-mounted electromagnetic relays.
Further, if electric power is supplied thereto at a low voltage in a conventional manner even when the number of the electrically-driven parts is increased, the diameter of a wire harness for transfer of electric power becomes large. This results in increase in weight and cost of the wire harness. It has, thus, been proposed that a battery having a terminal voltage of 40 to 60 volts (V) should be used instead of the presently-used battery having a terminal voltage of 12 to 16 V.
Therefore, to control the supply of electric power to the electrically-driven actuator, currently, an electromagnetic relay capable of cutting-off a low voltage is used. Conversely, in future, the use of an electromagnetic relay capable of cutting-off a high voltage will be needed.
However, when high voltage is cut-off by the electromagnetic relay for cutting off low voltage, an arcing time at the cut-off becomes long, so that welding or sticking between the contacts of the electromagnetic relay easily occurs. Consequently, the service life of the contacts thereof becomes short.
There has been publicly known a method of broadening the space between the contacts of the electromagnetic relay so as to extend the service life of the contacts thereof. However, when the space therebetween is broadened, there is the necessity for increasing the size not only the contacts thereof but also of an electromagnetic coil so as to increase a magnetic force for operating the contacts thereof. Thus, the size of the entire electromagnetic relay inevitably becomes big.
The present invention is accomplished to solve the aforementioned problems. Accordingly, an object of the present invention is to provide an electromagnetic relay that has contacts, whose service life can be long, and can be miniaturized even when used for cutting-off a high voltage.
To achieve the foregoing object, according to a first aspect of the present invention, there is provided an electromagnetic relay that comprises an iron core, a coil wound around the iron core, an armature attracted by the iron core when electric power is supplied to the coil, a first common contact driven by the armature, a first make contact contacted with the common contact when the armature is attracted by the iron core, and an arc suppressing means for suppressing an occurrence of arc between the common contact and the make contact when the common contact is separated from the make contact by stopping supply of electric power to the coil.
Thus, according to this first aspect, an occurrence of arc between the common contact and the make contact is suppressed when the common contact is separated from the make contact. Consequently, the abrasion of the contacts is reduced. Further, the service life of the electromagnetic relay becomes long. Additionally, the space between the contacts is decreased, so that miniaturization of the electromagnetic relay is achieved.
According to a second aspect of the present invention, the arc suppressing means comprises at least one second common contact driven by the armature, at least one second make contact contacted with each of the at least one second common contact when the armature is attracted to the iron core, and a series-connecting means not only for serially connecting at least one first keying circuit, each of which comprises a first common contact and a first make contact, and at least one second keying circuit to each other, each of which comprises a second common contact and a second make contact, but also for serially connecting the serial connection of the at least one second keying circuit to the at least one first keying circuit.
Thus, according to this second aspect, an occurrence of arc at the time of circuit interruption is suppressed by serially connecting two or more keying circuits, each of which comprises one common contact and one make contact.
According to a third aspect of the present invention, the arc suppressing means comprises arc extinguishing means for extinguishing an arc generated between the common contact and the make contact by using a magnetic field which is caused by an electric current generated when the supply of electric power to the coil is stopped.
Thus, according to this third aspect, an arc generated between the contacts is extinguished by the magnetic field which is caused by the back electromotive force generated when the circuit is opened, and an electric current flowing in the arc.